Seller financing question

[Brandon Sizemore]

My grandmother seller financed her house to a woman for $650 a month for 20 years. The woman lived in it for a couple years and moved out and let her sister move in. They filed to get section 8 housing assistance and my grandmother signed for it. My question is was anything dealing with section 8 a violation of the contract or do I need to find out more specifics of the contract? It seems shady to me that she moved out and moved her sister with section 8 housing in but I didn't know if there was anything wrong with that or not.